As far as I can tell this makes the (context) thing you implemented before pretty redundant or is it worth keeping?
On Fri, Sep 16, 2011 at 6:39 PM, Alexander Burger <a...@software-lab.de>wrote: > Hi all, > > from time to time, the issue of symbol namespaces (or the lack of them) > in PicoLisp is brought up again. > > Personally, I think that namespaces (that is, different sets of interned > symbols in different contexts) may confuse more than they do really > help. > > But with transient symbols we do already have a certain kind of > namespaces, implicit by the lexical (source file) context. So I decided > to go ahead, and implement "named" symbol namespaces ... if we regard > transient symbols as residing in the own anonymous namespaces. > > This feature is available only in the 64-bit version. It could perhaps > be implemented also in Ersatz and MiniPicoLisp, but unfortunately not in > the 32-bit version, because of its different symbol table mechanism. > > > The underlying concepts are very simple. Only a single new function was > added, 'symbols', and a new global 'pico' holding the initial (default) > symbol namespace. > > If 'symbols' is never called, everything should work as before. > > Calling it without arguments > > : (symbols) > -> pico > > returns the current namespace. > > > If you call it with the name of a new namespace and the name of an > existing namespace > > : (symbols 'myNames 'pico) > -> pico > > the following happens: The symbol 'myNames' (existing in the current > namespace) receives a _copy_ of the namespace 'pico', and is made the > new current one. Check: > > : (symbols) > -> myNames > > > After a namespace is created that way, it is independent from other > namespaces. New symbols will be added here, and deleting symbols (with > 'zap') will not influence other namespaces. > > Thus, a symbol will not be garbage collected as long as it is referred > to from at least one namespace. Symbols from other namespaces, when > visible in data structures, will appear as transient symbols. > > > If you call 'symbols' with a single argument, it should be an existing > namespace, and this will be set to be the new current one. > > : (symbols 'pico) > -> myNames > > The previously current namespace is returned. > > Check: > > : (symbols) > -> pico > > Fiddling around with symbols named "Foo": > > : (zero Foo) > -> 0 > > : (symbols 'myNames) > -> pico > > : (one Foo) > -> 1 > > : Foo > -> 1 > > : (symbols 'pico) > -> myNames > > : Foo > -> 0 > > To access a symbol in another namespace, we can use a tilde character > separating a namespace from a symbol. The tile was chosen because it > possibly does not conflict with the rest of the PicoLisp syntax. > > : myNames~Foo > -> 1 > > : (setq myNames~Bar 'myNames~Foo) > -> "Foo" > > : Bar > -> NIL > > : (symbols 'myNames) > -> pico > > : Bar > -> Foo > > This syntax can also be chained, e.g. myNames~yourNames~foo > > > I have released a new testing version as a draft. Documentation and unit > tests are still missing, though. > > Any opinions? > > Cheers, > - Alex > -- > UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe >
